Efficacy of hydrodilatation in frozen shoulder: a systematic review and meta-analysis

Abstract Introduction It is unclear whether hydrodilatation is beneficial in the management of frozen shoulder compared with other common conservative management modalities. This systematic review evaluates the efficacy of hydrodilatation for the management of frozen shoulder. Sources of data A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. An extensive search of PubMed, Embase, Scopus, Cochrane Central, Web of Science and CINAHL databases using multiple keyword combinations of ‘shoulder’, ‘rotator’, ‘adhesive capsulitis’, ‘hydrodilatat*’, ‘distension’ since inception of the databases to June 2023 was implemented. Areas of agreement Hydrodilatation leads to at least transient more marked improvements in shoulder disability and passive external rotation compared with intra-articular corticosteroid injections. Areas of controversy Hydrodilatation improves passive external rotation in the longer term. Moreover, hydrodilatation may be a preferable option over manipulation under anaesthesia, given its lower cost and better patient convenience. Growing points Intensive mobilization after hydrodilatation is a promising adjuvant treatment option for patients suffering from a frozen shoulder. Areas timely for developing research Although current evidence suggests that hydrodilatation provides a transient improvement in disability in patients with frozen shoulder, its clinical relevance remains unclear. Further research is necessary to establish its role in the management of the condition.


Introduction
Frozen shoulder, sometimes referred to as adhesive capsulitis, is an insidious musculoskeletal condition that affects the glenohumeral joint.It is characterized by the formation of scar tissue, adhesions and capsular thickening within the shoulder. 1 ,2Frozen shoulder has a reported prevalence of 2-5% in the general population, rising to 20% in individuals with diabetes mellitus. 3Typically, patients present with excruciating pain and reduced passive and active range of motion (ROM) of the glenohumeral joint.Symptoms generally last from 6 months to 2 years.Most patients demonstrate spontaneous resolution of symptoms, and thus conservative management is commonly advised. 4urrently, there exists a plethora of conservative management options for patients with frozen shoulder, including analgesia, corticosteroids (oral or intra-articular), physiotherapy, acupuncture, manipulation, suprascapular nerve blockade and hydrodilatation. 5First proposed in 1965 by Andren and Lundberg, intra-articular hydrodilatation attempts to expand the joint space through the sheer hydraulic pressure exerted by the injectate. 6However, given the marked disability caused by frozen shoulder, some patients may forgo the less invasive hydrodilatation and instead opt for more invasive surgery.This is a possible consequence of the perceived slow nature of symptom improvement with conservative approaches. 7Additionally, there remains ambiguity surrounding the effectiveness of hydrodilatation as a treatment method. 8m et al. compared hydrodilatation to corticosteroid injections alone and identified improvements in shoulder pain and ROM. 9 However, the results of this study were limited given the high risk of bias.On the contrary, Corbiel et al. and Jacobs et al. found no significant differences when assessing the same treatment modalities. 10,11Furthermore, many studies have examined the efficacy of hydrodilatation amid other treatment options, and thus its specific effects have not always been assessed. 12e effectiveness of hydrodilatation may well be short-lived, 10,11 as no large study has addressed this particular aspect of the intervention. 10Hydrodilatation may potentially lower the prevalence of long-term impairments; however, it remains challenging to determine the number of patients suffering from residual deficiencies. 10Most recently, Saltychev et al. demonstrated statistically significant symptomatic improvements with the use of hydrodilatation when assessing its effectiveness in the management of frozen shoulder.However, this effect was deemed not to be clinically relevant. 5hus, amid the incongruent results in the literature, more research is warranted.Nonetheless, hydrodilatation is recommended as part of the patient care pathway co-produced by the British Elbow and Shoulder Society and British Orthopaedic Association. 12is review evaluates the current evidence on the efficacy of hydrodilatation for frozen shoulder.This study builds on the previous systematic review by Saltychev et al.,  5 through the inclusion of recently published randomized controlled trials and prospective and retrospective studies.

Study design
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 were used to conduct and report this review. 13Our Population, Intervention, Comparison and Outcome framework was as follows: • Participants: adults, with frozen or painfully stiff shoulders, suffering from discomfort that limits both active and passive glenohumeral joint motions.
-Primary: assessment of pain and function or disability.-Secondary: ROM, complications and any others.

Search strategy
Computer searches were conducted on PubMed, Embase, Scopus, Cochrane Central, Web of Science and CINAHL electronic databases from inception to June 18, 2023 for articles assessing hydrodilatation in patients with frozen shoulder.The goal was to increase the search strategy's sensitivity to increase the likelihood that all relevant studies would be obtained. 14,15ur search clause for the PubMed search was '(shoulder OR rotator OR adhesive capsulitis) AND (hydrodilatat * OR distension).'When conducting searches on the different databases, similar clauses were utilized.We adjusted the search strategy from a previous systematic review 5 to accommodate our own needs.The search was restricted to humans only, and the reference management software EndNote was used to organize its results.The relevance of the cited studies' references was also examined.A step-by-step process, which involved team meetings to improve the search strategy and settle disagreements, was utilized to ensure that the searches were producing relevant studies. 16

Study screening
All references were downloaded from the Rayyan reference management software, and duplicates were removed before screening the title and abstract.The full texts of the remaining articles were examined after two authors (DP and RH) independently assessed the titles and abstracts.A consensus meeting between the two authors was organized to settle disputes that arose during research screening and selection.If no consensus could be reached, the senior author (NM) was contacted for a final decision.

Study selection
Only peer-reviewed journals were considered.There were limited restrictions on the study design within the selection criteria, which increased the likelihood of identifying pertinent studies.Thus, randomized controlled trials, prospective and retrospective comparative studies and case series were included.Level I-IV studies, according to the Oxford Centre for Evidence Based Medicine, were identified and included in our analysis.The hydrodilatation technique and follow-up period had to be well described in all included studies, which had to use at least one validated clinical outcome score or assess change in ROM.Studies needed to be published in English, and had to have recruited at least 10 adult participants.Exclusion criteria were reviews, case reports, experiments on animals, cadavers or in vitro and letters to editors.We also excluded articles with no information on hydrodilatation intervention, diagnosis, follow-up, clinical examination and statistical analysis.
To prevent bias, all authors read, evaluated and discussed the included and excluded studies and the relative list of references.The senior investigator (NM) made the final decision if there was a disagreement among the investigators on the inclusion and exclusion criteria.

Data extraction
Data extracted from each study included the following: author name, study year; study design (level of evidence); number of patients (shoulders); mean age (range) (years); diabetes mellitus diagnosis; Coleman Methodology Score (CMS); imaging assessment; duration of symptoms (average) (months); outcome measures (time intervals); regimen and modification of the distension arms; comparative intervention arm; hydrodilatation technique; and complications.Data were entered in a custom Excel spreadsheet by all the investigators independently.A standardized form, based on the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0,Chapter 7, was used for data extraction for the meta-analysis. 17Discussions with the senior author (NM) allowed the resolution of any discrepancies.

Quality assessment
The methodological quality was assessed according to the CMS. 18Modifications of the CMS were made to make it pertinent for the systematic review of frozen shoulder (Table 1).Each study was scored by two reviewers (DP and RH) independently and in duplicate for each of the criteria adopted to give a total CMS between 0 and 100.A study design that eliminates the impact of chance, bias and confounding variables would receive a score of 100.Disagreements were resolved by discussion.The CMS is divided into sections, each of which is based on a component of the CONSORT statement (for randomized controlled trials) with modifications to accommodate various study designs.

Statistical analysis
The meta-analysis was performed using Review Manager, version 5.4 (The Cochrane Collaboration).The I 2 statistic was used to test for statistical heterogeneity and was assessed as follows: 0% < I 2 < 25%, low heterogeneity; 25% < I 2 < 50%, moderate heterogeneity; and I 2 > 50%, high heterogeneity. 18his effectively describes the percentage of variation across studies originating more from heterogeneity than from chance.We used the random-effects model because outcome measurements were taken at different time points, and the different phases of frozen shoulder increases the risk of heterogeneity.Data for quantitative analysis were extracted at twotime points: the first follow-up post-intervention and the last follow-up post-intervention.The Egger's test and a funnel plot were used to evaluate the publication bias.
When just the interquartile range (IQR) was provided, IQR/1.35 was used to calculate the standard deviation (SD).According to the Cochrane Handbook for Systematic Review of Interventions Version 5.1.0,Chapter 7, the mean was presumed to be the same as the median when only the median was given. 17SD was computed as (max-min)/4 when only the range was given.Cohen's d-a standardized mean difference (SMD) in variable change between groups-was used to calculate the effect sizes.
Variables were measured by the SMD with 95% confidence intervals (95% Cis).Data synthesis was initiated for each included study by combining pertinent reported outcomes stratified by pain, disability and ROM at pre-determined time points (earliest and latest follow-ups).
In all analyses, a P-value < 0.05 was considered statistically significant.Sensitivity analysis was conducted to evaluate the reliability of the effects.One study was eliminated at that time, and studies with very heterogeneous findings were also eliminated.

Study identification and selection
Our initial search yielded 1234 articles, with a total of 452 left following the removal of duplicates.We then screened the titles and abstracts of the remaining articles and retained 54 articles for full-text evaluation, which resulted in 39 studies (Fig. 1).

Demographics
A total of 2623 participants and 2632 shoulders were included.The number of participants recruited in each study varied from 22 to 250.Data on the

Study identification and selection
A total of 20 studies (51.3%) used imaging, such as ultrasound or magnetic resonance imaging, to confirm the diagnosis of frozen shoulder.The hydrodilatation procedures were performed under ultrasound or fluoroscopic guidance.In 21 studies, the hydrodilatation was administered through the posterior approach, in 13 through the anterior approach, and in 1 using both anterior and posterior approaches.Inclusion and exclusion criteria were overall quite similar across most articles.The volume of mixture injected for hydrodilatation ranged from 9 to 100 mL.Typically, the hydrodilatation mixture consisted of corticosteroids, local anaesthetic and normal saline solution, and only one study used a combination of hyaluronic acid and lidocaine. 45Intra-articular corticosteroid injections were the most commonly utilized reference therapy.Arthroscopic capsular release (ACR), manipulation under anaesthesia (MUA), placebo (arthrogram), general physical therapy and treatment as usual (i.e.physical therapy and oral medication) were also used (Table 3).

Outcomes measurements
The included studies used several outcome measures.The visual analogue score (VAS) was used in

Quality assessment
The average CMS score was 63, indicating that the overall quality of the included studies was fair.Table 2 provides the actual values of the CMS.Interrater reliability was calculated between the mean values of CMS calculated by two authors (DP and RH).Cohen's kappa coefficient (k) was 0.779661, indicating substantial agreement for the first round of methodological quality assessment.The intrarater reliability was k = 0.864111 and 0.915309 for DP and RH respectively, indicating almost perfect agreement.

Complications
The included studies reported transient complications such as flushing, local depigmentation of the skin, loss of sensory and motor control in the affected arm, loss of sleep, nausea, dizziness, 31,35,36,40,50,55 hypotensive syncope 37 and afterinjection pain. 9,24,26,34,36In one patient, hydrodilatation was abandoned from unbearable pain during the procedure. 28Two studies reported one patient each with a glenohumeral joint infection. 44,50

Meta-analysis of the studies evaluating the effect of capsular distension versus corticosteroid alone
There was no significant benefit of intra-articular corticosteroid injection alone compared with capsular distension at the first follow-up post-intervention (SMD, 0.09; 95% CI, −0.27 to 0.45) and at the last follow-up post-intervention (SMD, −0.02; 95% CI, −0.21 to 0.17) when pain scores were evaluated (Fig. 2).
Moreover, there were no statistically significant differences in passive forward flexion, abduction or internal rotation at both time points (Figs 5-Fig.7).
The Cochrane Handbook Chapter 10 advises that tests for funnel plot asymmetry should only be used if a minimum of 10 studies are included in the metaanalysis.As this threshold was not reached, funnel plot asymmetry was not calculated. 17

Quantitative analysis of the studies not included in the meta-analysis
The pooled effect sizes of studies not included in the meta-analysis where intra-articular corticosteroid was not used as a control are shown in forest plots (Figs 8-10).All comparisons were not statistically significant when evaluating the pooled effect size.
Park et al. 42 showed large effect sizes at the outcome measurements for pain, disability and external rotation for the earliest follow-ups post-intervention.In that study, a combination of intensive mobilization after hydrodilatation was compared with general physiotherapy.

Discussion
The present systematic review investigated the effectiveness of hydrodilatation for frozen shoulder in terms of pain, shoulder disability and ROM, which were considered proxy indicators of therapeutic effects.Hydrodilatation demonstrated transient improvements in shoulder disability during the early follow-up periods.Additionally, significant improvements in passive external rotation were observed at the earliest and latest follow-ups.When comparing the pooled effects of hydrodilatation    to other reference treatments, such as MUA, ACR and general physiotherapy, no significant differences were identified.
Contracture of the coracohumeral ligament is considered the predominant pathology in frozen shoulder.During image-guided hydrodilatation, leakage of contrast agents into the subscapularis bursa is often a sign of capsular rupture. 11This occurrence suggests that, in comparison with the posterior capsule, the anterior joint capsule is less resistant to the stretching forces of the injectate, which may account for the improvements in passive external rotation.However, more research is required to confirm this hypothesis.Various  epidemiological studies have identified a link between diabetes mellitus and frozen shoulder. 57 -59ndeed, this systematic review included a total of 224 individuals (18%) with diabetes mellitus.
In a previous Cochrane review, Buchbinder et al. identified one study comparing hydrodilatation versus placebo, and found improvements in shoulder pain and ROM.However, there was insufficient evidence to suggest that hydrodilatation prevailed over intra-articular corticosteroid injections, which are well reported for the treatment of a frozen shoulder. 10he combination of the two treatments may induce a synergistic effect, the former abating glenohumeral joint inflammation and the latter facilitating joint cavity expansion. 11ost of the evidence in the present systematic review is derived from comparisons between hydrodilatation versus intra-articular corticosteroid injections alone.The results of this review support previous studies, which also found statistically   significant but transient improvements in shoulder disability and passive external rotation. 11Thus, clinicians must balance the immediate improvements in disability and external rotation with the possible negative consequences of hydrodilatation, such as the acute pain following joint capsular rupture.However, we did also identify improvements in passive external rotation at the latest follow-ups, contrary to the findings of previous studies. 11urthermore, mixed results were evidenced when comparing the efficacy of hydrodilatation and MUA. Park et al. found statistically significant improvements in pain, disability and external rotation for MUA when compared with hydrodilatation. 42n the other hand, Quraishi et al. identified that hydrodilatation provided statistically significant improvements in pain compared with MUA in the earliest follow-up periods. 51However, there were no significant differences in pain scores at late followups and in terms of disability outcome measures.Therefore, MUA should be considered secondary to hydrodilatation given its uncertainty regarding its superiority.Also, MUA is a relatively expensive inpatient procedure, whereas hydrodilatation is an outpatient treatment which does not require anaesthesia.Other recognized drawbacks of MUA include humeral fractures, isolated infraspinatus paralysis, brachial plexus traction injuries and rotator cuff tears. 47,49,51

Limitations
This investigation presents several limitations.Firstly, as frozen shoulder of all durations was examined as a whole, we could not determine the best way to treat each of the stages of frozen shoulder.Secondly, both within and across trials, different volumes of hydrodilatation fluid were utilized.As a result, we were unable to assess the association between injectate volume and its clinical efficacy.Therefore, to standardize the delivery of hydrodilatation in future studies, researchers and clinicians should adhere to recently published guidelines. 60Thirdly, our secondary outcomes included several shoulder ROM components that might lead to erroneous positive results.As a result, any favourable secondary outcomes should be carefully assessed and supported by further research.
Fifthly, publication bias was not assessed, as we had less than ten studies in the meta-analysis.Sixthly, our meta-analysis software (Review Manager 5.4) was not able to differentiate the specific outcomes measures and comparative treatments on the forest plots for the studies by Park (2014) and Yoon (2016) (Figs 8-10).This made it impossible to visually distinguish which comparative treatment demonstrated superior efficacy.
Furthermore, only a relatively few outcomes, namely changes in pain intensity, disability and improvements in ROM, were used to assess the efficacy of hydrodilatation.As a result, several potentially important outcomes were not considered, including patient satisfaction and incidence of complications.Also, the role of concurrent physiotherapy on the effects of hydrodilatation was not measured since patients' post-intervention exercise routines differed among the included trials and were not described in sufficient detail.Therefore, future research should include standardized rehabilitation protocols, and ensure that the regimen is adequately described. 61Finally, doubts regarding the accuracy of injections should be considered as we did not differentiate the study's results based on image-versus anatomical landmark-guided injections.

Conclusion
Hydrodilatation may provide early improvements of disability in addition to short-and long-term improvements in passive external rotation in frozen shoulder.However, there is comparable effectiveness of glenohumeral joint hydrodilatation and intra-articular corticosteroid injection when assessing most long-term outcomes.Hydrodilatation is a promising alternative treatment to the more expensive surgery.Clinicians must manage patient expectations appropriately given the wide number of reported complications.Finally, well-designed, appropriately powered RCTs, with a low risk of bias, are required to confirm the relevance and validity of hydrodilatation in the management of frozen shoulder.

Fig. 2
Fig.2Early after intervention (A) and at the end of the study (B).Forest plot of the standardized mean differences of pain improvement comparing hydrodilatation and intra-articular corticosteroid injection.

Fig. 3
Fig.3Early after intervention (A) and at the end of the study (B).Forest plot of the standardized mean differences of disability improvement comparing hydrodilatation and intra-articular corticosteroid injection.

Fig. 4
Fig.4 Early after intervention (A) and at the end of the study (B).Forest plot of the standardized mean differences of improvements in passive external rotation with the use of hydrodilatation or an intra-articular corticosteroid injection.

Fig. 5
Fig.5 Early after intervention (A) and at the end of the study (B).Forest plot of standardized mean differences of improvements in passive forward flexion with the use of hydrodilatation or an intra-articular corticosteroid injection.

Fig. 6
Fig.6 Early after intervention (A) and at the end of the study (B).Forest plot of standardized mean differences of improvements in passive abduction with the use of hydrodilatation or an intra-articular corticosteroid injection.

Fig. 7
Fig.7 Early after intervention (A) and at the end of the study (B).Forest plot of the standardized mean differences of improvements in passive internal rotation with the use of hydrodilatation or an intra-articular corticosteroid injection.

Fig.
Fig. Early after the intervention (A) and at the end of the study (B).Forest plots of the standardized mean differences of improvements in pain with usage of hydrodilatation and/or different reference treatments.

Fig.
Fig. Early after the intervention (A) and at the end of the study (B).Forest plots of the standardized mean differences of improvements in disability with usage of hydrodilatation and/or different reference treatments.

Fig. 10
Fig.10 Early after the intervention (A) and at the end of the study (B).Forest plots of standardized mean differences of improvements in external rotation with usage of hydrodilatation and/or different reference treatments.

Table 1
Modified Coleman Methodology ScorePart A: Only one score to be given for each of the seven sections

Table 2
Details of included articles

Table 3
Frozen shoulder management

Table 3 Continued
in group D. (SPADI) in 18 studies; the Oxford Shoulder Score (OSS) in seven studies; the Disabilities of the Arm, Shoulder and Hand (DASH) in three studies; and the Constant-Murley score in five studies.